Debugging commands available at a leashed event are of two basic types. Some
commands cause execution of the debugger to proceed as far as the next leashed
event; others perform some operation and then expect another command at the
same event. Commands through abort are in the former category;
the remaining commands (starting with unify) are in the latter.
exit - Exit in success. This is the normal behavior at an EXIT event; elsewhere it forces the goal to succeed immediately, without further computation. redo - Redo the goal. This is the normal behavior at a REDO event; elsewhere it forces the goal that just succeeded to be redone. fail - Fail the goal. This is the normal behavior at a FAIL event; elsewhere it forces the goal to fail even if it would have succeeded. step - Step into a goal or clause. At a CALL or REDO event, for a predicate written in Prolog, this will cause a CLAUSE event for each clause; for control structure predicates or at a CLAUSE event, this will leash each of the subgoals of the control structure or clause. next - Move on to the next clause of the current predicate, abandoning further work on this clause leap - Cancel stepping through a goal or clause initiated by step. The execution of the goal or clause proceeds as if a call or redo had been given initially. over - Start the current goal over from the beginning. abort - Abort to top-level. unify - Prompt for a term and then unify the current goal with it. If unification succeeds, any bindings established remain in effect through the rest of the execution of the goal. writeq - Write out the current goal (with any variable instantiations done so far) using writeq display - Display the current goal (with any variable instantiations done so far) using display vars - Write out variable instantiations done so far for the current goal. break - Enter a break loop, which will be terminated by EOF. +trace - Turn on exhaustive tracing, as by trace/0. -trace - Turn off exhaustive tracing, as by notrace/0. parent - Display the clause of which the current goal is a subgoal. history - Display the history of calls leading up to the current goal. ? - Display a help message listing available commands and a brief description.